SU693232A1 - Electron paramagnetic resonance radiospectrometer resonator - Google Patents

Description

(54) RADIOSPECTROMETER ELECTRON PARAMAGNETIC RESONANCE RESONATOR is a triple dielectric resonator resonator: ceramics + quartz probe + pressure transmitting fluid. Moreover, the pressure transferring fluid is not present locally near the sample, but in the whole free space of the cavity volume. Under extreme conditions, at high pressures and low temperatures, the liquid changes its dielectric properties, which leads to a sharp change in the parameters of the resonator, in particular, a deterioration of the quality factor of the resonator, and consequently, to a deterioration in the sensitivity of the spectrometer as a whole. In addition, the use of aluminum as the metal walls of the resonator, the electrical conductivity of which is about 2 times worse than the electrical conductivity of copper at room temperature and 4 times worse at low temperatures, causes a corresponding number of times worse Q-factor compared with resonators having copper walls. The connection of the microwave input with a resonator is constant and does not make it possible to select the optimal operating conditions of the spectrometer in the measurement process. It is also necessary to note the small sizes of the samples under study (0.25-0.5 mm), which makes it possible to study only substances containing a high concentration of paramagnetic centers, a considerable complexity of their manufacture in the form of spheres, the impossibility of simultaneously examining two samples without disassembling the resonator. The use of the Noi mode limits the smallest possible diameter of the resonator to 14 mm, which does not allow to reduce the dimensions of the high-pressure vessel, thereby reducing the achievable upper pressure limit and complicates their use in the case of low temperatures. In addition, a dielectric filling made of ceramics contains a significant number of extraneous paramagnetic centers, which makes it difficult to obtain useful information. The aim of the invention is to expand the functionality of the resonator, reduce its size, increase the upper pressure limit in the high-pressure vessel, as well as reduce the complexity of the experiments. Expansion of functionality lies in the fact that with the help of this resonator it is possible to measure the spectra of electron paramagnetic resonance, spn-lattice relaxation of weakly and strongly concentrated substances with paramagnetic impurities under conditions of normal and high hydrostatic pressure. The goal is achieved by the fact that the filler is optically conjugated by one end to the obturator butt, the test specimen is placed on the other end of the filler, the sleeve is made of galvanic copper with internal dimensions corresponding to the size of the placeholder, and the holes for the passage of the hydroenvironment are made from the end of the sleeve. In order to eliminate parasitic EPR impurities, the aggregate is made of a sapphire single crystal. In order to ensure the operation of the cavity at two frequencies of the same mode, the single crystal of sapphire is oriented in such a way that its main optical axis lies in the plane of the obturator end face; the filler is made in the form of a cylindrical body, and the sample under study is placed inside the annular ring; Katets's schayba is made of leucosapphire; for measuring pressure and assessing the hydrostaticity of the medium, the annular washer is made of ruby; To simultaneously examine two samples, two slots were made on the side surface of the filler on opposite sides. FIG. 1 and 2 show two embodiments of the resonator; in fig. 3 is a layout of a step-groove on the side surface of the dielectric core body. The design of the proposed resonator (Fig. 1) consists of a obturator 1, in the inner hole of which in the low-level zone there is a movable coaxial2 With a communication loop, which, depending on the processing of the resonator, reaches the surface or INPUTS into the hemispherical notch 3 of the dielectric core sapphire 4, ring washer 5, test sample 6, and sleeve cage 7. A resonator with a solid dielectric die. The implant uses the HIM mode, which gives the smallest dimensions at a given frequency, as filler leucosapphire monocrystal, one of its ends is optically conjugated with the butt of the high-pressure vessel obturator, and the sample under study is placed at the other end of the fill, the metal sleeve is electroplated from copper, with internal dimensions corresponding to the size of the filler, and the holes for the passage of the liquid placed in her butt. The sleeve — a liner at the same time as its main function — the function of creating a closed metal coating with a resonator coupling hole — also plays the role of fixing the dielectric filler on the obturator of a high-pressure vessel. The accuracy of matching the inner dimensions of the sleeve-cage with the dimensions of the resonator body (dielectric filler) and the high purity of its inner surface v 2 is achieved by electroplating (electrolytic) copper build-up on the mandrel of the required purity, exactly corresponding to the shape and size of the resonator. Compaction of the obturator itself when installed in a pressure vessel is achieved by known methods.

The necessary connection of the resonator with the microwave is achieved by changing the immersion in the inner channel of the coaxial obturator with the coupling loop, and turning the loop around the axis changes the direction of polarization. A hemispherical recess can be made from leucosapphire to increase the coupling in the body of the resonator.

The use of a leucosapphire monocrystal as a filler allows, firstly, eliminating parasitic EPR impurities, which is important for measuring spin-lattice relaxation, secondly, by using dielectric constant anisotropy, it is possible to operate the resonator at two different frequencies at the same mode, the crystal is oriented in such a way that its main optical axis is in the plane of the end face of the resonator.

The goal is also achieved by placing the test specimen at the end of the filler inside the annular ring made of either the filler material or ruby. When using a ruby ring plate, the pressure is simultaneously measured and the environment is hydrostatic.

Measurements using the proposed measurement cell are carried out as follows. A resonator assembled on the obturator 1, including monocrystal 4, sample 6, case 7, is placed in a high-pressure vessel in which pressure is generated by known methods. After which the vessel is placed in a cryostat. After adjusting the spectrometer to the frequency of the resonator under pressure, proceed to the slow cooling of the entire device. This cooling procedure provides near-hydrostatic pressure in the vessel as long as the temperature changes. The necessary connection is achieved by immersing the coaxial 2 in a hemispherical recess. Because of the measurement of the electron spin-mesh relaxation time, the pulse saturation method is used. The EPR signal was saturated with an additional, saturating klystron, the pulse modulation of which is carried out by applying to the reflector & klystron and pulses from the generator.

The cylindrical resonator works on the Hill mode. The samples under study are usually made in the form of cylinders and are placed on the lower end of the resonator in the neck5 of leucosapphire or ruby. The height of the washer is about 2 mm, its internal diameter is 5-6 mm, however a sample of arbitrary shape can be placed in the resonator.

In some cases, modifications may be made to the proposed resonator with a dielectric core.

in the form of a parallelepiped, cut from a single crystal sapphire. The disadvantage of cylindrical resonators operating on the Hi 1, 1/2, 3 .... / modes, when the sample is located in the washer at the bottom of the resonator, means that when studying the angular dependence of the spectrum, the signal intensity changes. A rectangular resonator operating on the Hioi mode is free from this drawback, with notch steps 8 and 9 on the side surface, which are the place

the location of the samples (Fig. 2). With this arrangement of samples, the advantage is that Hoi.Hi is satisfied, while rotating the magnetic field Ho, and the signal intensity does not change. If necessary, two samples can also be simultaneously studied in a rectangular cavity. The ruby crystal can be located in one groove on the side surface of the filler body, then the sample under study is placed in another groove. FIG. Figure 3 shows the layout of the step-groove on the lateral surface of the body of a single crystal of sapphire, oriented in such a way that the main optical axis. Cj lay in the plane of the butt.

Since, in the proposed construction, the dielectric constants of sapphire are different EI i and are in the plane of the resonator end, the resonator becomes S two-frequency. Since the cavity dimensions are constant, then.

G1 / L1 U „/ ILYYA, 4 / U

so, for example, at a HRH of 11.6,, 9.5 for AUOj, then fz, //, 10.3 GHz.

 A step in the body of the resonator, cut at an angle of 45 ° to the axis C3, is the location of the samples. Such placement of the sample allows to obtain the same intensity of the EPR signal from the sample.

5 at two different frequencies. Two samples can be simultaneously examined in the resonator, for this purpose one more step is cut from the opposite side, parallel to the first. By turning the loop of communication, at the lowest frequency f i, the required polarization is achieved, i.e. the plane of the loop coincides with the axis 1, and by selecting the required bond by immersing the loop, measurements are taken. Measurements at a higher frequency are made by turning the loop of the connection through 90 °.

Claims (2)

S The pressure and the degree of non-hydrostaticity of the medium using a ruby crystal are measured by the following method. In a ruby crystal, the initial splitting parameter D varies linearly with pressure: K 21.3 MHz / kbar. By the displacement of the lines of the EPR spectrum of the ruby (Ci-bA1r.Oz), but by changing the value of the initial splitting constant D, the pressure value in the high-pressure bomb is judged. The width of the 1st and 3rd lines will indicate the presence of non-hydrostatic pressure in the chamber and its value can be estimated as follows: dp - ij: HL where H1 is the width of the 1st line at normal pressure, NG-width of the 1st line at pressure P Since the value of D does not depend on temperature, all difficulties in measuring pressure at low temperatures are removed. The choice of material with low dielectric losses, a high degree of accuracy of the resonator surface treatment, the use of a material with high electrical conductivity and the purity of its internal surface as a metal surface made it possible to obtain a quality factor of 3000 described resonators close to the maximum possible (5000) at a frequency of 9.3 GHz room temperature. The range of permissible operating pressures for these resonators is of the order of 30 kbar in devices creating cylinder-pressure-type pressures. Kerosene oil is used as a hydroenvironment for the mixture. The proposed design of the measuring cell (resonator) of an EPR radio spectrometer provides it with high physicotechnical characteristics, which make it possible to study both electron spin-grating relaxation and EPR spectra under conditions of high hydrostatic pressure. The use of the proposed design of the resonator under normal conditions allows one to obtain a significant gain in the uniformity and intensity of the external magnetic field. Another advantage of the proposed resonator is that on the same resonator, dual-frequency EPR measurements are possible on samples that are under the same conditions — microwave field, pressure, temperature. Using a polarizer in combination with traditional waveguide coupling to a resonator in radio spectroscopy extends the range of use of the proposed resonator, because with this solution it becomes possible to saturate the EPR signal at one frequency and observe the recovery signal at another. 1. An electron paramagnetic resonance radio spectrometer resonator containing a solid-state dielectric filler and a test specimen placed inside a metal sleeve connected to the end of the shutter with a hole for the passage of a pressure transmitting medium, characterized in that, in order to expand the functionality, reduce the dimensions of the resonator and an increase in the upper limit of the hydrostatic medium, the filler is optically conjugated by its one end to the obturator butt, The sample is placed at the other end of the filler, the sleeve is made of galvanic copper with internal dimensions corresponding to the size of the filler, and the holes for the passage of hydro-media are made from the end of the sleeve. 2. A resonator according to claim 1, characterized in that, in order to eliminate spurious EPR impurities, the aggregate is made of a single crystal of sapphire. 3. Rezonator on PP. 1 and 2, characterized in that in order to ensure that the resonator operates at two frequencies of the same mode, the sapphire single crystal is oriented in such a way that its main optical axis lies in the plane of the obturator end face. 4. Rezonator on PP. 1-3, characterized in that the aggregate is made in the form of a cylindrical body, and the sample under study is placed inside the annular ring. 5. A resonator according to claims 1-4, characterized in that the ring washer is made of synthetic sapphire. 6. The resonator according to Claim 4, characterized in that the ring washer is made of ruby for measuring pressure and evaluating the hydrostaticity of the medium. 7. The resonator according to claim 1, characterized in that two slots are made on the side surface of the core from opposite sides to simultaneously examine two samples. Sources of information taken into account during the examination 1. G. Neilo, V. I. Petrenko and G. A. Tsintsadze. PTE, No. 5, 1972, p. 210. 2.I.P. Kaminow, R. V. Zopez. Phys. Rev. 123, No. 4, 1961, p. 1122. (prototype).